http://www.hindawi.comThe latest articles from Hindawi Publishing Corporation© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2009/835789.htmlA new dual-input differential input active integrator using a current differencing buffered amplifier (CDBA) is proposed. A multiplier element is appropriately used in the circuit whose control voltage (Vc) tunes the integrator time constant (τ) electronically. The design of a voltage controlled quadrature oscillator (VCQO) based on the proposed integrator had been satisfactorily implemented. A new type of measurement for the tuning error of the oscillator based on the Nyquist plot is presented that shows an error of only 2% at fo≈ 1 MHz with Total Harmonic Distortion (THD) less than 3%.R. Nandi, Mousiki Kar, and Sagarika Das© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2009/789171.htmlThis paper describes a current-mode third-order quadrature oscillator based on current differencing transconductance amplifiers (CDTAs). Outputs of two current-mode sinusoids with 90° phase difference are available in the quadrature oscillator circuit. The oscillation condition and oscillation frequency are orthogonal controllable. The proposed circuit employs only grounded capacitors and is ideal for integration. Simulation results are included to confirm the theoretical analysis.Jiun-Wei Horng© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2009/378086.htmlPoly(aniline-co-o-toluidine) (PANI-co-POT) thin films were deposited on indium tin oxide- (ITO-) coated glass substrates by electrochemical polymerization under cyclic voltammetric conditions from aniline-co-o-toluidine monomer in an aqueous solution of HCl as a supporting electrolyte. These measurements showed that the optical band gap of the copolymer films is on the order of 2.65 eV. On the other hand, ITO/PANI-co-POT/Al devices were fabricated by thermal evaporation of Aluminum circular electrodes on the as-deposited PANI-co-POT films. The Current-Voltage characteristics of these devices are nonlinear. The diode parameters were calculated from I-V characteristics using the modified Shockley equation. The C-F characteristics were also measured.A. Elmansouri, N. Hadik, A. Outzourhit, A. Lachkar, A. Abouelaoualim, M. E. Achour, A. Oueriagli, and E. L. Ameziane© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2009/437130.htmlComposite materials were made by mixing powders of Ba1−xSrxTiO3 (x=0.2 and 0.4) ceramics and epoxy resin with various volume fractions (vol%). Dielectric measurements of these composites were performed as a function of filler ratio in the range 100–360°K at 10 KHz. The dielectric constant of the composite increased with increasing volume fraction varies slightly with temperature. The 20 vol% of BST(0.4)-epoxy composite had the highest dielectric constant of 19.4 and dielectric loss tangent of 0.027. Among the dielectric mixing models presented, the model of Lichtenecker shows the best fit to the experimental data for both composites.N. Hadik, A. Outzourhit, A. Elmansouri, A. Abouelaoualim, A. Oueriagli, and E. L. Ameziane© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2009/824531.htmlA model description for the representation of one-dimensional piecewise-linear characteristics is presented. The model can be denoted as a decomposed one, because the independent and dependent variables of the PWL characteristic are treated separately. It is also called iterative, because the particular representation of each segment of the PWL characteristic depends on the value of only one parameter included in the mathematical formulation, it gives the possibility of modeling both, univalued and multivalued PWL characteristics.Victor Jimenez-Fernandez, Luis Hernandez-Martinez, and Arturo Sarmiento-Reyes© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2009/609298.htmlA new low-cost electronic control circuit actuator is proposed for minimizing the bouncing times of an AC permanent magnet (PM) contactor after two contacts closing. The proposed new actuator overcomes the bouncing problem of an uncontrollable restrictions imposed by previously conventional AC electromagnetic (EM) contactor based on the minimization of kinetic energy prior to two contacts impact. By choosing the closing phase angle of coil voltage on purpose, the bouncing problems of the movable contact during the closing process are then overcome. The using life of contacts is then prolonged and their operating reliability is improved as well. In order to validate the feasibility and effectiveness of the proposed method here, several simulation and experimental procedures were performed on a prototype of AC PM contactor in the laboratory. Testing results actually showed that bouncing problem of contactor's contacts during the closing process was to be controlled by using the proposed technology.Chieh-Tsung Chi© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2009/595324.htmlThis comment is related to the recently published article “Active and Passive Electronic Components” by S. Maheshwari (2007), which presents single current differencing buffered amplifier (CDBA) and current-controlled current differencing buffered amplifier- (CC-CDBA-) based first-order voltage-mode (VM) all-pass filtering (APF) sections. The paper is reviewed, and additional first-order APF realizations have been proposed.Abhirup Lahiri© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2009/987304.htmlA new voltage-mode quadrature oscillator using two differential difference current conveyors (DDCCs), two grounded capacitors, and three grounded resistors is presented. The proposed oscillator provides the following advantages: the oscillation condition and oscillation frequency are orthogonally controlled; the oscillation frequency is controlled through a single grounded resistor; the use of only grounded capacitors and resistors makes the proposed circuit ideal for IC implementation; low passive and active sensitivities. Simulation results verifying the theoretical analysis are also included.Montree Kumngern and Kobchai Dejhan© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/905628.htmlThis work simulates the nonlinear electromechanical behavior of different electrostatic microactuators. It applies the differential quadrature method, Hamilton's principle, and Wilson-θ integration method to derive the equations of motion of electrostatic microactuators and find a solution to these equations. Nonlinear equation difficulties are overcome by using the differential quadrature method. The stresses of electrostatic actuators are determined, and the residual stress effects of electrostatic microactuators are simulated.Ming-Hung Hsu© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/623970.htmlA new wide input range square-rooting circuit is presented. The proposed circuit consists of a dual translinear loop, an absolute value circuit, and current mirrors. A current-mode technique is used to provide wide input range with simple circuitry. The output signal of the proposed circuit is the current which is proportional to the square root of input current. The proposed square-rooting circuit was confirmed by using PSpice simulator program. The simulation results demonstrate that the proposed circuit provides the excellent temperature stability with wide input current range.Montree Kumngern and Kobchai Dejhan© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/537069.htmlThis paper presents novel multilayer tuneable high Q-filters based on hairpin resonators including ferroelectric materials. This configuration allows the miniaturization of these filters to a size that makes them suitable for chip and package integration and narrow-band applications. The main focus was miniaturizing filters with coupled loops using multilayer dielectric substrates. A further goal was to increase the quality factor of these distributed filters by embedding high dielectric materials in a multilayer high- and low-k (dielectric constant) substrate that is supported by LTCC technology. An improved W-shape bandpass filter was proposed with a wide stopband and approximately 5% bandwidth.Aly H. Aly, Badawy El-Sharawy, and Adalbert Beyer© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/320956.htmlT. S. Kalkur, Tibor Berceli, and Fahrettin Yakuphanoglu© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/632549.htmlThis paper describes the design and fabrication of a Ka Band PLL DRO having a fundamental oscillation frequency of 19.250 GHz, used as local oscillator in the low-noise block of a down converter (LNB) for an EHF band receiver. Apposite circuital models have been created to describe the behaviour of the dielectric resonator and of the active component used in the oscillator core. The DRO characterization and measurements have shown very good agreement with simulation results. A good phase noise performance is obtained by using a very high Q dielectric resonator.S. Coco, F. Di Maggio, A. Laudani, and I. Pomona© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/693263.htmlA compact wideband stacked patch antenna is presented for the applications of GPS systems. This antenna covers the L1, L2, and L5 GPS bands of operating frequencies 1.575, 1.227, and 1.176 GHz, respectively. High permittivity dielectric materials are used to minimize the antenna dimensions. The obtained antenna is of dimensions 32×18×2.117 mm. To verify the design, the time dependence field distribution, the scattering parameters, and the radiation pattern are presented. The scattering parameters show that the antenna operates at the GPS frequencies with lower than −10 dB. The finite difference time domain (FDTM) with the perfect matched layer (PML) is used in the present analysis.Maher M. Abd Elrazzak and M. F. Alsharekh© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/742050.htmlA novel layout of leaky-wave antennas based on tapered design has been proposed and investigated. The new tapered leaky-wave antenna (LWA) was designed running a simple procedure which uses an FDTD code, and using a suitable metal walls down the centerline along the length of the antenna connecting the conductor strip and the ground plane, which allows to use only half of the structure, the adoption of a simple feeding, and the reduction of sidelobes. The good performance of this new tapered microstrip LWA, with reference to conventional uniform microstrip LWAs, is mainly the wider band of 33% for VSWR <2, higher gain (12 dBi), and higher efficiency (up to 85%). Furthermore, from the theoretical analysis we can see that, decreasing the relative dielectric constant of the substrate, the bandwidth of the leaky-wave antenna becomes much wider, improving its performance.Onofrio Losito© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/539618.htmlWe show a technique for external direct current (DC) control of the amplitudes of limit cycles both in the Phase-shift and Twin-T oscillators. We have found that amplitudes of the oscillator output voltage depend on the DC control voltage. By varying the total impedance of each oscillator oscillatory network, frequencies of oscillations are controlled using potentiometers. The main advantage of the proposed circuits is that both the amplitude and frequency of the waveforms generated can be independently controlled. Analytical, numerical, and experimental methods are used to determine the boundaries of the states of the oscillators. Equilibrium points, stable limit cycles, and divergent states are found. Analytical results are compared with the numerical and experimental solutions, and a good agreement is obtained.J. P. Dada, J. C. Chedjou, and S. Domngang© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/356049.htmlThis paper presents new compact bandstop filters (BSFs) with extended upper passbands. In the basic proposed filter configuration, the conventional quarter-wavelength open-stub resonators are replaced with equivalent two-section stepped impedance resonators. Transmission line analysis is used to determine the dimensions of the equivalent stepped impedance sections. The filter structure is analyzed using a full wave electromagnetic (EM) simulator and then realized at 2.3 GHz band. Experiments have also been done to validate the performance of the design concept. Compared with the conventional quarter-wavelength-based bandstop filter, significant extensions of the upper passband beyond 9 GHz and 40% size reduction are achieved. Two other variations of the proposed basic BSF with further size reduction (more than 60%) are implemented and their measured performances are verified.Majeed A. S. Alkanhal© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/391745.htmlThis paper presents the design, construction, and testing of grounded frequency selective surface (FSS) array as a diffuser for destroying millimeter wave coherence which is used to eliminate speckle in active millimeter wave imaging. To create stochastically independent illumination patterns, we proposed a diffuser based on random-phase distributions obtained by changing the incident frequency. The random-phase diffuser was obtained by mixing up the phase relations between the cells of a deterministic function (e.g., beam splitter). The slot length of FSS is the main design parameter used to optimize the phase shifting properties of the array. The critical parameters of the diffuser array design, such as phase relation with slot lengths, losses, and bandwidth, are discussed. We designed the FSS arrays with finite integral technique (FIT), fabricated by etching technique, and characterized the S-parameters with a free-space MVNA, and measured the radiation patterns with a BWO in motorized setup.Saiful Islam, Johan Stiens, Gert Poesen, Irina Jaeger, and Roger Vounckx© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/745368.htmlThe stop-band filter with the new band-rejection element is proposed. The element is a coaxial waveguide with the slot in the centre conductor. In the frame of this research, the numerical and experimental investigations of the amplitude-frequency characteristics of the filter are carried out. It is noted that according to the slot parameters the two typical resonances (half-wave and quarter-wave) can be excited. The rejection band of the single element is defined by the width, depth, and dielectric filling of the slot. Fifth-order Chebyshev filter utilizing the aforementioned element is also synthesized, manufactured, and tested. The measured and simulated results are in good agreement. The experimental filter prototype exhibits the rejection band 0.86 GHz at the level −40 dB.R. E. Chernobrovkin, I. V. Ivanchenko, A. M. Korolev, N. A. Popenko, and K. Yu. Sirenko© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/247958.htmlThe main steps for characterization and measurement of microwave absorbent materials in the 1–10 GHz range are introduced. The coaxial reflection-transmission type of material parameter measurement is analyzed in detail and the main measurement error is corrected. The microscopic material particle parameter measurement concept is also presented using different mixing rule laws to determine the material parameters of the single particles from the macroscopic parameters. Two-dimensional FDTD simulations have been used to model the behavior of mixed electric and magnetic type of material.Lajos Nagy© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/542929.htmlThe problem of side lobe suppression (SLS) in printed antenna arrays has been investigated in the paper. Influence of several factors that make difficult design and realization of antenna arrays with relatively high SLS has been analyzed. We introduced a new type of printed antenna array with symmetrical pentagonal dipoles and symmetrical tapered feed network with Chebyshev distribution enabling SLS better than 34 dB in E-plane. Agreement between simulated and measured results is very good. The antenna is suitable for integration with other microwave circuits. Presented antenna is low cost and very simple for realization.Aleksandar Nešić, Ivana Radnović, and Zoran Mićić© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/369421.htmlActive and passive realization of Fractance device of order 1/2 is presented. The crucial point in the realization of fractance device is finding the rational approximation of its impedance function. In this paper, rational approximation is obtained by using continued fraction expansion. The rational approximation thus obtained is synthesized as a ladder network. The results obtained have shown considerable improvement over the previous techniques.B. T. Krishna and K. V. V. S. Reddy© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/275357.htmlThe dynamic performance of wide-bandgap 4H-SiC based double drift region (p++ p n n++) IMPATT diode is simulated for the first time at terahertz frequency (0.7 Terahertz) region. The simulation experiment establishes the potential of SiC based IMPATT diode as a high power (2.5×1011 Wm−2) terahertz source. The parasitic series resistance in the device is found to reduce the RF power output by 10.7%. The effects of external radiation on the simulated diode are also studied. It is found that (i) the negative conductance and (ii) the negative resistance of the diode decrease, while, the frequency of operation and the quality factor shift upward under photoillumination. Holes in 4H-SiC based IMPATT are found to dominate the modulation activities. The inequality in the magnitude of electron and hole ionization rates in the semiconductors may be correlated with these findings.Moumita Mukherjee, Nilratan Mazumder, and Sitesh Kumar Roy© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/134805.htmlSilicon-based radio-frequency integrated circuits are becoming more and more competitive in wide-band frequency range. An essential component of these ICs is on-chip (integrated) transformer. It is widely used in mobile communications, microwave integrated circuits, low-noise amplifiers, active mixers, and baluns. This paper deals with the design, simulation, and analysis of novel fractal configurations of the primary and secondary coils of the integrated transformers. Integrated stacked transformers, which use fractal curves (Hilbert, Peano, and von Koch) to form the primary and secondary windings, are presented. In this way, the occupied area on the chip is lower and a number of lithographic processes are decreased. The performances of the proposed integrated transformers are investigated with electromagnetic simulations up to 20 GHz. The influence of the order of fractal curves and the width of conductive lines on the inductance and quality factor is also described.Goran Stojanović, Milan Radovanović, and Vasa Radonić© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/859052.htmlTo explain the relevant changes in the electron cyclotron resonance ion source behaviour for small variations of the exciting radiation frequency, we determine the spatial distribution of the field within the cavity for every resonant mode.Fabrizio Consoli, Luigi Celona, Giovanni Ciavola, Santo Gammino, Fabio Maimone, Rocco Salvatore Catalano, Sebastiano Barbarino, David Mascali, and Livia Tumino© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2007/080839.abs.htmlYalin Lu, Weili Zhang, and Min Qiu© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/816969.htmlAn E-field probe has been developed for EMC immunity tests performed in closed space. The leads are flexible resistive transmission lines. Their influence on the field distribution is negligible. The probe has an isotropic reception from 100 MHz to 18 GHz; the sensitivity is in the 3 V/m–10 V/m range. The device is an accessory of the EMC test chamber. The readout of the field magnitude is carried out by personal computer, which fulfils also the required corrections of the raw data.Béla Szentpáli, István Réti, Ferenc B. Molnár, János Farkasvölgyi, Károly Kazi, Zoltán Mirk, Aurél Sonkoly, and Zoltán Horváth© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2007/024084.abs.htmlTransmission metallic gratings having the shape of converging-diverging channel (CDC) give an extra degree of freedom to exhibit enhanced transmission resonances. By varying the gap size at the throat of CDC, the spectral locations of the transmission resonance bands can be shifted close to each other and have high transmittance in a very narrow energy band. Hence, the CDC shape metallic gratings can lead to almost perfect transmittance for any desired wavelength by carefully optimizing the metallic material, gap at the throat of CDC, and grating parameters. In addition, a cavity surrounded by the CDC shaped metallic grating and a one-dimensional (1D) photonic crystal (PhC) can lead to an enhanced emission with properties similar to a laser. The large coherence length of the emission is achieved by exploiting the coherence properties of the surface waves on the gratings and PhC. The new multilayer structure can attain the spectral and directional control of emission with only p-polarization. The resonance condition inside the cavity is extremely sensitive to the wavelength, which would then lead to high emission in a very narrow wavelength band. Such simple 1D multilayer structure should be easy to fabricate and have applications in photonic circuits, thermophotovoltaics, and potentially in energy efficient incandescent sources.Arvind Battula, Yalin Lu, R. J. Knize, Kitt Reinhardt, and Shaochen Chen© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2008/247171.htmlThe voltage-mode universal biquadratic filter and sinusoidal quadrature oscillator based on the use of current differencing buffered amplifiers (CDBAs) as active components have been proposed in this paper. All the proposed configurations employ only two CDBAs and six passive components. The first proposed CDBA-based biquad configuration can realize all the standard types of the biquadratic functions, that is, lowpass, bandpass, highpass, bandstop, and allpass, from the same topology, and can also provide orthogonal tuning of the natural angular frequency (ωo) and the bandwidth (BW) through separate virtually grounded passive components. By slight modification of the first proposed configuration, the new CDBA-based sinusoidal quadrature oscillator is easily obtained. The oscillation condition and the oscillation frequency are independently adjustable by different virtually grounded resistors. The sensitivity analysis of all proposed circuit configurations is shown to be low. PSPICE simulations and experimental results based upon commercially available AD844-type CFAs are included, which confirm the workability of the proposed circuits.Worapong Tangsrirat, Tattaya Pukkalanun, and Wanlop Surakampontorn© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/apec/2007/093548.abs.htmlA design of parallel-coupled microstrip bandpass filters without spurious resonance is presented. Two different techniques are used to eliminate this response at twice the passband frequency (2fo). The first one is based on usage of suspended substrate, while the second is carried out by shorting the parallel-coupled lines to the ground plane through two shorting walls. The numerical results show that a broadband filter can be obtained by the suppression of the spurious response. The finite difference time domain (FDTD) with the perfect matched layer (PML) is used in the present analysis. The obtained results are compared with the available published data and good agreements are found.Maher M. Abd-Elrazzak© 2010, Hindawi Publishing Corporation. All rights reserved.